The 1876 Portuguese banking crisis, triggered by a partial default on Spanish bonds, offers a compelling historical case of widespread bank runs in a pre-central bank setting, where no major bank failures occurred despite severe liquidity pressures. Using unique hand-collected data and narrative evidence, paired with a difference-in-differences framework, we analyze the liquidity-driven nature of the runs and document significant declines in deposits and subsequent reductions in credit provision for banks exposed to Spanish sovereign debt. Preemptive and sizeable government interventions - liquidity provision, currency suspension, and payment moratoria - successfully averted systemic collapse. However, regions more affected by the runs experienced lasting economic scarring, highlighting the uneven consequences of financial crises.